Skip to content

⚡️Understand  Wistek Store promotions  before placing orders

Wish Lists Cart
0 items

Knowledge

how many 350 watt solar panels are needed to produce 15 kwh annually

by chenli fang 15 Aug 2025 0 Comments

If you're wondering how many 350 watt solar panels you need to produce 15 kWh annually, you've come to the right place. This guide will help you figure out your exact needs based on geography, efficiency, and system design, ensuring you get the most accurate answer for planning your solar installation.

lithium ion battery discharge curve

Before diving into calculations, it's critical to understand what 350 watt solar panels actually mean and why they're so commonly used for residential and small commercial solar projects.

What Does "350 Watt" Mean?

When you see a 350 watt solar panel, the 350 watts represents its maximum rated output under standard test conditions (STC). This means:

Peak sunlight (typically 1000 W/m²)

Panel temperature at 25°C

Air mass of 1.5

In real life, you won't get that perfect 350 W output all the time due to clouds, angle, temperature, and other factors.

Why 350 Watt Panels Are Popular

These panels strike a balance between cost, efficiency, and size:

High enough wattage to reduce the number of panels you need

Affordable due to mass production

Reasonable size (around 1.7–2 m²) so they fit most rooftops

For people asking “how many 350 watt solar panels for 15 kWh per year,” this wattage is a practical choice.

To figure out how many 350 watt solar panels you need for 15 kWh annually, you need to understand the difference between power and energy:

Power: Watts (W) – instantaneous output

Energy: Kilowatt-hours (kWh) – cumulative over time

A single 350 W panel produces 350 W only in peak sun. Over a day or a year, total energy depends on sun hours.

Daily vs. Annual Production

Example:

If you get 4 peak sun hours per day:

Daily energy = 350 W × 4 = 1.4 kWh

Annual energy = 1.4 kWh/day × 365 = 511 kWh

That's over 500 kWh from one panel in a year under good conditions—far more than 15 kWh! So for most places, you'd need only a fraction of a panel to produce 15 kWh annually.

But let’s dig in deeper to ensure you get precise, location-specific answers.

>>See also What can I use to separate my LFP Cells andor line my metal box with to protect my cells

Your location dramatically impacts solar production. Let’s look at average annual production per 350 W panel in different climates.

Example Locations

Arizona (USA): 5.5–6.5 sun hours/day

~700–830 kWh/year/panel

Germany: 2.5–3.5 sun hours/day

~320–450 kWh/year/panel

UK: 2–3 sun hours/day

~250–400 kWh/year/panel

India (good areas): 4.5–6 sun hours/day

~575–765 kWh/year/panel

Conclusion

Even in poor solar regions, a single 350 W panel will often exceed 15 kWh annually. So you typically need just one panel to cover that, with capacity to spare.

We can’t ignore real-world losses:

Inverter efficiency: ~95%

Wiring losses: 1–3%

Dust/soiling: 2–5%

Temperature losses: 5–10%

A conservative derating factor is ~0.75–0.85.

Adjusted Production Example

Assume 4 sun hours/day:

Ideal = 350 × 4 × 365 = 511 kWh/year

Derated at 0.8 = 409 kWh/year

That’s still massively over 15 kWh/year.

Now the big answer: in nearly all real-world cases, you technically need less than one 350 watt solar panel to produce 15 kWh annually. Even in low-sunlight areas, a single panel comfortably exceeds 15 kWh/year.

Formula

General formula:

Annual kWh=Panel Watts×Peak Sun Hours/day×365×Derating Factor

Despite the math, you can’t install 0.05 of a panel! Here’s what to consider:

Minimum System Size

Install at least one panel—even if you only need 15 kWh/year. Benefits:

Simpler design

Cost-effective (panels are sold in whole units)

Leaves extra energy for other uses

Battery Storage

If you only need 15 kWh/year intermittently (e.g., for lighting a shed), consider pairing the single 350 watt solar panel with a small battery bank:

12V 100Ah battery stores ~1.2 kWh

15 kWh/year = ~1.25 kWh/month

One battery can smooth out supply even in cloudy weeks.

You might think “one panel is cheap,” but the full system cost includes:

Panel itself: ~$100–$250

Mounting: $50–$150

Inverter (if grid-tied or AC load): $100–$300

Charge controller (off-grid DC): $30–$100

Battery (if needed): $100–$500

For such a small annual load, the panel is often the cheapest part.

Roof Space

Each panel ≈ 1.7–2 m²

One panel is easy to fit on almost any structure

Orientation and Tilt

South-facing (Northern Hemisphere)

North-facing (Southern Hemisphere)

Tilt optimized for latitude

Even small deviations reduce annual output, so plan carefully.

Producing such a small amount annually doesn’t remove the need for maintenance:

Clean panels every few months

Inspect wiring and connectors

Check battery health if off-grid

Even a single 350 watt solar panel deserves proper care to deliver 15 kWh reliably.

If you want to future-proof your system, consider:

Installing two panels even if you only need one

Extra energy for future loads

Redundancy

Modular design

Add more panels as needed

15 kWh/year is tiny for solar. Most residential systems aim for thousands of kWh/year, so you have room to grow.

Your small system still reduces carbon emissions:

Grid power often ~0.5 kg CO₂/kWh

15 kWh/year ≈ 7.5 kg CO₂ avoided

While small, it’s a step toward sustainability. Installing even one 350 watt solar panel can help meet your green goals.

>>See also Is it safe to discharge Lead Acid batteries to 20%

You may wonder:

Why not 250W or 450W?

350W is a mid-size sweet spot:

Cost per watt is low

Compatible with many inverters

Easy to handle and install

If your supplier only has 400W panels, you’ll need even fewer to meet 15 kWh/year.

Check local incentives:

Tax credits

Rebates

Net metering

Even a small system with one 350 watt solar panel may qualify for incentives that offset the entire install cost.

Can a single 350 watt solar panel power my home?

Not alone—it might produce 300–800 kWh/year. Average home uses 8,000–12,000 kWh/year. You’d need 10–30 panels.

Can I just buy part of a panel?

No—panels are sold as whole units. You can’t buy 0.05 of a panel.

What happens to extra energy?

If grid-tied: export for credit.
If off-grid: store in batteries or waste it.

In summary, if you’re asking:

How many 350 watt solar panels are needed to produce 15 kWh annually?

The answer is: typically less than one panel is enough! But since you can’t buy part of a panel, you’ll need to install one panel minimum. That single panel will vastly exceed your 15 kWh/year target, providing you with surplus energy for other small uses, storage, or grid credit.

Investing in 350 watt solar panels for small loads is still a smart choice for sustainability, resilience, and cost savings over time.

Even for such a small need, planning carefully ensures you get the best results—from selecting quality hardware to proper orientation and maintenance.

If you're ready to get started, check local providers for 350 watt solar panels and see how easy it is to meet (and exceed) that 15 kWh/year goal!

lithium ion battery discharge curve
Prev Post
Next Post

Leave a comment

All blog comments are checked prior to publishing

Someone recently bought a
[time] ago, from [location]

Thanks for subscribing!

This email has been registered!

Shop the look

Choose Options

Recently Viewed

Edit Option
Back In Stock Notification
Compare
Product SKURatingDescription Collection Availability Product Type Other Details
Terms & Conditions

This website is operated by Wistek. Throughout the site, the terms “we”, “us” and “our” refer to Wistek. Wistek offers this website, including all information, tools and Services available from this site to you, the user, conditioned upon your acceptance of all terms, conditions, policies and notices stated here

By visiting our site and/ or purchasing something from us, you engage in our “Service” and agree to be bound by the following terms and conditions (“Terms of Service”, “Terms”), including those additional terms and conditions and policies referenced herein and/or available by hyperlink. These Terms of Service apply to all users of the site, including without limitation users who are browsers, vendors, customers, merchants, and/ or contributors of content. Please read these Terms of Service carefully before accessing or using our website. By accessing or using any part of the site, you agree to be bound by these Terms of Service. If you do not agree to all the terms and conditions of this agreement, then you may not access the website or use any Services. If these Terms of Service are considered an offer, acceptance is expressly limited to these Terms of Service. Any new features or tools which are added to the current store shall also be subject to the Terms of Service. You can review the most current version of the Terms of Service at any time on this page. We reserve the right to update, change or replace any part of these Terms of Service by posting updates and/or changes to our website. It is your responsibility to check this page periodically for changes. Your continued use of or access to the website following the posting of any changes constitutes acceptance of those changes. Our store is hosted on Shopify Inc. They provide us with the online e-commerce platform that allows us to sell our products and Services to you. SECTION 1 - ONLINE STORE TERMS By agreeing to these Terms of Service, you represent that you are at least the age of majority in your state or province of residence, or that you are the age of majority in your state or province of residence and you have given us your consent to allow any of your minor dependents to use this site. You may not use our products for any illegal or unauthorized purpose nor may you, in the use of the Service, violate any laws in your jurisdiction (including but not limited to copyright laws). You must not transmit any worms or viruses or any code of a destructive nature. A breach or violation of any of the Terms will result in an immediate termination of your Services. SECTION 2 - GENERAL CONDITIONS We reserve the right to refuse Service to anyone for any reason at any time. You understand that your content (not including credit card information), may be transferred unencrypted and involve (a) transmissions over various networks; and (b) changes to conform and adapt to technical requirements of connecting networks or devices. Credit card information is always encrypted during transfer over networks. You agree not to reproduce, duplicate, copy, sell, resell or exploit any portion of the Service, use of the Service, or access to the Service or any contact on the website through which the Service is provided, without express written permission by us. The headings used in this agreement are included for convenience only and will not limit or otherwise affect these Terms. SECTION 3 - ACCURACY, COMPLETENESS AND TIMELINESS OF INFORMATION We are not responsible if information made available on this site is not accurate, complete or current. The material on this site is provided for general information only and should not be relied upon or used as the sole basis for making decisions without consulting primary, more accurate, more complete or more timely sources of information. Any reliance on the material on this site is at your own risk. This site may contain certain historical information. Historical information, necessarily, is not current and is provided for your reference only. We reserve the right to modify the contents of this site at any time, but we have no obligation to update any information on our site. You agree that it is your responsibility to monitor changes to our site. SECTION 4 - MODIFICATIONS TO THE SERVICE AND PRICES Prices for our products are subject to change without notice. We reserve the right at any time to modify or discontinue the Service (or any part or content thereof) without notice at any time. We shall not be liable to you or to any third-party for any modification, price change, suspension or discontinuance of the Service. SECTION 5 - PRODUCTS OR SERVICES (if applicable) Certain products or Services may be available exclusively online through the website. These products or Services may have limited quantities and are subject to return or exchange only according to our Refund Policy: [LINK TO REFUND POLICY] We have made every effort to display as accurately as possible the colors and images of our products that appear at the store. We cannot guarantee that your computer monitor's display of any color will be accurate. We reserve the right, but are not obligated, to limit the sales of our products or Services to any person, geographic region or jurisdiction. We may exercise this right on a case-by-case basis. We reserve the right to limit the quantities of any products or Services that we offer. All descriptions of products or product pricing are subject to change at anytime without notice, at the sole discretion of us. We reserve the right to discontinue any product at any time. Any offer for any product or Service made on this site is void where prohibited. We do not warrant that the quality of any products, Services, information, or other material purchased or obtained by you will meet your expectations, or that any errors in the Service will be corrected. SECTION 6 - ACCURACY OF BILLING AND ACCOUNT INFORMATION We reserve the right to refuse any order you place with us. We may, in our sole discretion, limit or cancel quantities purchased per person, per household or per order. These restrictions may include orders placed by or under the same customer account, the same credit card, and/or orders that use the same billing and/or shipping address. In the event that we make a change to or cancel an order, we may attempt to notify you by contacting the e‑mail and/or billing address/phone number provided at the time the order was made. We reserve the right to limit or prohibit orders that, in our sole judgment, appear to be placed by dealers, resellers or distributors. You agree to provide current, complete and accurate purchase and account information for all purchases made at our store. You agree to promptly update your account and other information, including your email address and credit card numbers and expiration dates, so that we can complete your transactions and contact you as needed. For more details, please review our Refund Policy: [LINK TO REFUND POLICY] SECTION 7 - OPTIONAL TOOLS We may provide you with access to third-party tools over which we neither monitor nor have any control nor input. You acknowledge and agree that we provide access to such tools ”as is” and “as available” without any warranties, representations or conditions of any kind and without any endorsement. We shall have no liability whatsoever arising from or relating to your use of optional third-party tools. Any use by you of the optional tools offered through the site is entirely at your own risk and discretion and you should ensure that you are familiar with and approve of the terms on which tools are provided by the relevant third-party provider(s). We may also, in the future, offer new Services and/or features through the website (including the release of new tools and resources). Such new features and/or Services shall also be subject to these Terms of Service. SECTION 8 - THIRD-PARTY LINKS Certain content, products and Services available via our Service may include materials from third-parties. Third-party links on this site may direct you to third-party websites that are not affiliated with us. We are not responsible for examining or evaluating the content or accuracy and we do not warrant and will not have any liability or responsibility for any third-party materials or websites, or for any other materials, products, or Services of third-parties. We are not liable for any harm or damages related to the purchase or use of goods, Services, resources, content, or any other transactions made in connection with any third-party websites. Please review carefully the third-party's policies and practices and make sure you understand them before you engage in any transaction. Complaints, claims, concerns, or questions regarding third-party products should be directed to the third-party. SECTION 9 - USER COMMENTS, FEEDBACK AND OTHER SUBMISSIONS If, at our request, you send certain specific submissions (for example contest entries) or without a request from us, you send creative ideas, suggestions, proposals, plans, or other materials, whether online, by email, by postal mail, or otherwise (collectively, 'comments'), you agree that we may, at any time, without restriction, edit, copy, publish, distribute, translate and otherwise use in any medium any comments that you forward to us. We are and shall be under no obligation (1) to maintain any comments in confidence; (2) to pay compensation for any comments; or (3) to respond to any comments. We may, but have no obligation to, monitor, edit or remove content that we determine in our sole discretion to be unlawful, offensive, threatening, libelous, defamatory, pornographic, obscene or otherwise objectionable or violates any party’s intellectual property or these Terms of Service. You agree that your comments will not violate any right of any third-party, including copyright, trademark, privacy, personality or other personal or proprietary right. You further agree that your comments will not contain libelous or otherwise unlawful, abusive or obscene material, or contain any computer virus or other malware that could in any way affect the operation of the Service or any related website. You may not use a false e‑mail address, pretend to be someone other than yourself, or otherwise mislead us or third-parties as to the origin of any comments. You are solely responsible for any comments you make and their accuracy. We take no responsibility and assume no liability for any comments posted by you or any third-party. SECTION 10 - PERSONAL INFORMATION Your submission of personal information through the store is governed by our Privacy Policy, which can be viewed here: [LINK TO PRIVACY POLICY] SECTION 11 - ERRORS, INACCURACIES AND OMISSIONS Occasionally there may be information on our site or in the Service that contains typographical errors, inaccuracies or omissions that may relate to product descriptions, pricing, promotions, offers, product shipping charges, transit times and availability. We reserve the right to correct any errors, inaccuracies or omissions, and to change or update information or cancel orders if any information in the Service or on any related website is inaccurate at any time without prior notice (including after you have submitted your order). We undertake no obligation to update, amend or clarify information in the Service or on any related website, including without limitation, pricing information, except as required by law. No specified update or refresh date applied in the Service or on any related website, should be taken to indicate that all information in the Service or on any related website has been modified or updated. SECTION 12 - PROHIBITED USES In addition to other prohibitions as set forth in the Terms of Service, you are prohibited from using the site or its content: (a) for any unlawful purpose; (b) to solicit others to perform or participate in any unlawful acts; (c) to violate any international, federal, provincial or state regulations, rules, laws, or local ordinances; (d) to infringe upon or violate our intellectual property rights or the intellectual property rights of others; (e) to harass, abuse, insult, harm, defame, slander, disparage, intimidate, or discriminate based on gender, sexual orientation, religion, ethnicity, race, age, national origin, or disability; (f) to submit false or misleading information; (g) to upload or transmit viruses or any other type of malicious code that will or may be used in any way that will affect the functionality or operation of the Service or of any related website, other websites, or the Internet; (h) to collect or track the personal information of others; (i) to spam, phish, pharm, pretext, spider, crawl, or scrape; (j) for any obscene or immoral purpose; or (k) to interfere with or circumvent the security features of the Service or any related website, other websites, or the Internet. We reserve the right to terminate your use of the Service or any related website for violating any of the prohibited uses. SECTION 13 - DISCLAIMER OF WARRANTIES; LIMITATION OF LIABILITY We do not guarantee, represent or warrant that your use of our Service will be uninterrupted, timely, secure or error-free. We do not warrant that the results that may be obtained from the use of the Service will be accurate or reliable. You agree that from time to time we may remove the Service for indefinite periods of time or cancel the Service at any time, without notice to you. You expressly agree that your use of, or inability to use, the Service is at your sole risk. The Service and all products and Services delivered to you through the Service are (except as expressly stated by us) provided 'as is' and 'as available' for your use, without any representation, warranties or conditions of any kind, either express or implied, including all implied warranties or conditions of merchantability, merchantable quality, fitness for a particular purpose, durability, title, and non-infringement. In no case shall Wistek, our directors, officers, employees, affiliates, agents, contractors, interns, suppliers, Service providers or licensors be liable for any injury, loss, claim, or any direct, indirect, incidental, punitive, special, or consequential damages of any kind, including, without limitation lost profits, lost revenue, lost savings, loss of data, replacement costs, or any similar damages, whether based in contract, tort (including negligence), strict liability or otherwise, arising from your use of any of the Service or any products procured using the Service, or for any other claim related in any way to your use of the Service or any product, including, but not limited to, any errors or omissions in any content, or any loss or damage of any kind incurred as a result of the use of the Service or any content (or product) posted, transmitted, or otherwise made available via the Service, even if advised of their possibility. Because some states or jurisdictions do not allow the exclusion or the limitation of liability for consequential or incidental damages, in such states or jurisdictions, our liability shall be limited to the maximum extent permitted by law. SECTION 14 - INDEMNIFICATION You agree to indemnify, defend and hold harmless Wistek and our parent, subsidiaries, affiliates, partners, officers, directors, agents, contractors, licensors, Service providers, subcontractors, suppliers, interns and employees, harmless from any claim or demand, including reasonable attorneys’ fees, made by any third-party due to or arising out of your breach of these Terms of Service or the documents they incorporate by reference, or your violation of any law or the rights of a third-party. SECTION 15 - SEVERABILITY In the event that any provision of these Terms of Service is determined to be unlawful, void or unenforceable, such provision shall nonetheless be enforceable to the fullest extent permitted by applicable law, and the unenforceable portion shall be deemed to be severed from these Terms of Service, such determination shall not affect the validity and enforceability of any other remaining provisions. SECTION 16 - TERMINATION The obligations and liabilities of the parties incurred prior to the termination date shall survive the termination of this agreement for all purposes. These Terms of Service are effective unless and until terminated by either you or us. You may terminate these Terms of Service at any time by notifying us that you no longer wish to use our Services, or when you cease using our site. If in our sole judgment you fail, or we suspect that you have failed, to comply with any term or provision of these Terms of Service, we also may terminate this agreement at any time without notice and you will remain liable for all amounts due up to and including the date of termination; and/or accordingly may deny you access to our Services (or any part thereof). SECTION 17 - ENTIRE AGREEMENT The failure of us to exercise or enforce any right or provision of these Terms of Service shall not constitute a waiver of such right or provision. These Terms of Service and any policies or operating rules posted by us on this site or in respect to the Service constitutes the entire agreement and understanding between you and us and governs your use of the Service, superseding any prior or contemporaneous agreements, communications and proposals, whether oral or written, between you and us (including, but not limited to, any prior versions of the Terms of Service). Any ambiguities in the interpretation of these Terms of Service shall not be construed against the drafting party. SECTION 18 - GOVERNING LAW These Terms of Service and any separate agreements whereby we provide you Services shall be governed by and construed in accordance with the laws of Hong Kong. SECTION 19 - CHANGES TO TERMS OF SERVICE You can review the most current version of the Terms of Service at any time at this page. We reserve the right, at our sole discretion, to update, change or replace any part of these Terms of Service by posting updates and changes to our website. It is your responsibility to check our website periodically for changes. Your continued use of or access to our website or the Service following the posting of any changes to these Terms of Service constitutes acceptance of those changes. SECTION 20 - CONTACT INFORMATION Questions about the Terms of Service should be sent to us at wistekxr@gmail.com. Our contact information is posted below: wistekxr@gmail.com.
this is just a warning
Login
Shopping Cart
0 items

Before you leave...

Take 20% off your first order

20% off

Enter the code below at checkout to get 20% off your first order

CODESALE20

Continue Shopping